Thermal ink-jet (TIJ) printers and plotters typically include a TIJ pen cartridge which includes a reservoir of ink coupled to the TIJ print head. One type of cartridge includes a polymer foam disposed within the print reservoir so that the capillary action of the foam will prevent ink from leaking or drooling from the print head. In such a foam cartridge, an air-vented delivery system is provided wherein air enters the reservoir via a separate vent opening to replace ink which is dispensed from the reservoir through the print head.
A different type of TIJ cartridge has an ink reservoir which is ordinarily maintained under a sub-atmospheric or negative pressure so that ink will not leak or drool from the print head. Various types of ink reservoirs may be used including refillable ink reservoir cartridges which are mounted on the moveable printer carriage, throwaway replaceable cartridges which are mounted on the printer carriage, and remote or off-board ink reservoirs from which ink is brought to the print head on the printer carriage by tubing.
A collapsible ink reservoir for an ink-jet printer is disclosed in U.S. Pat. No. 4,422,084, issued Dec. 20, 1983, to Saito. Negative pressure is maintained in a polypropylene ink bag by various types of springs which bias the bag walls apart from each other. The springs may be mounted inside of or externally of the ink bag, but the spring pressure regulator construction does not result in substantially complete emptying of the ink bag and the bag itself is not carried on a printer carriage.
Another ink reservoir which achieves constant negative back pressure through an external spring or an elastomeric bladder is disclosed in U.S. Pat. No. 4,509,062, issued Apr. 2, 1985.
An ink-printer marketed as the Canon BJ800 printer had an off-axis reservoir connected to an ink separator by a tubing, which was connected to an ink cartridge. The printer relied on the negative pressure in the cartridge and air accumulator to draw ink from the off-axis reservoir to the print cartridge. A pump, used to pull air from the air accumulator and to prime the print head, may cause some ink to move through the tubing into the air separator.
Large format ink-jet printer/plotters such as the DESIGNJET series sold by Hewlett-Packard Company offer substantial improvements in speed over the conventional X-Y vector plotter. Ink-jet printer/plotters typically include a plurality of print cartridges, each having a print head with an array of nozzles. The cartridges are mounted in a carriage which is moved across the page in successive swaths. Each ink-jet print head has heater circuits which when activated cause ink to be ejected from associated nozzles. As the cartridge is positioned over a given location, a jet of ink is ejected from the nozzle to provide a pixel of ink at a desired location. The mosaic of pixels thus created provides a desired composite image.
Recently, full color ink-jet printer/plotters have been developed which comprise a plurality of ink-jet cartridges of diverse colors. A typical color ink-jet printer/plotter has four ink-jet print cartridges, one for black ink (K), and three for color inks, magenta (M), cyan (C) and yellow (Y). The colors from the three color cartridges are mixed to obtain a full spectrum of color. The cartridges are typically mounted in stalls within an assembly which is mounted on the carriage of the printer/plotter. The carriage assembly positions the ink-jet cartridges and typically holds the circuitry required for interface to the heater circuits in the ink-jet cartridges.
Large scale printer/plotters have been developed which use cartridges with internal spring-bag reservoirs. Because of the volume of ink used in creating many plots, as well as the heavy usage to which the devices are put, the user must intervene to replace cartridges whose internal reservoirs have been depleted of ink. This can lead to expensive waste if a large scale plot is commenced, but must be discarded because one or more of the cartridges runs out of ink. The print media on which such plots are made is typically relatively expensive. Moreover, time is lost in commencing a large plot only to have to discard the plot because one of the cartridges runs out of ink before the plot is finished.
Thus, there is a need in the art for systems and techniques for providing an increased supply of ink in printer/plotters employing negative pressure cartridges.